Direct Visualization of Incommensurate Charge-Lattice Order in Correlated Oxides

The strong coupling between charge, spin, and lattice generates complex correlated phases and, in many cases, ordered patterns that break the spatial symmetries of the crystal. Charge-order stripes are particularly noteworthy because they alter electronic transport, compete with unconventional superconductivity, or spawn novel magnetic orders. As demonstrated by various real space probes, mapping striped electronic modulations locally is a powerful approach for visualizing stripe formation, observing defects and excitations, and discerning broken symmetries. Direct, atomic-scale measurements of lattice degrees of freedom, however, are lacking. Here, we use cryogenic scanning transmission electron microscopy (STEM) to map picometer-scale lattice displacements associated with charge-ordering in manganites. We directly visualize temperature-dependent nanosocale inhomogeneity and the interplay between commensurate and incommensurate modulations. In particular, the real space structure of incommensurate charge order suggests a strong tendency to lattice-locked modulations interspersed with phase defects. These cryogenic STEM measurements reveal a novel methodology for exploring lattice coupling in other correlated systems such layered nickelates and transition-metal dichalcogenides.